Nuclear Magnetic Resonance (NMR) is a physical characteristic of numerous nuclides which permits their detection and chemical characterization by appropriate instruments. Recently NMR Scanners have been developed which allow in vivo detection and subsequent spatial localization (imaging) of several biologically important nuclides, particularly 1H and 31P. These techniques will be used to evaluate mammary neoplasia in animals and human patients. 1H imaging and measurements of spin density, T1 and T2 will be performed in a murine mammary model which expresses three distinct morphological states: 1) hyperplasia; 2) preneoplasia; and 3) adenocarcinoma. In addition, patients with various breast dysplasias will be studied. In each case, the NMR measurements will be correlated with clinical status, other conventional procedures such as mammography and CT, and histopathology. All in vivo studies (animal and human) will be followed up with in vitro determinations of the relaxation times of water protons in the involved tissues. Attempts will be made to obtain high resolution 31P spectra of the animal tissues. The results from all experiments will be analyzed to determine early changes in breast tissue which may provide useful information for the early detection of breast cancer in the human.